The precedence diagramming method (PDM) is the most common method of arranging the project work visually. The PDM puts the activities in boxes, called nodes, and connects the boxes with arrows. The arrows represent the relationship and the dependencies of the work packages. The following illustration shows a simple network diagram using PDM.
EXAM TIP PDM is also known as AON—activity-on-node. It's the most common approach to network diagramming, since it's used by most project management information systems, but can also be done manually.
Relationships between activities in a PDM constitute one of four different types (as shown in Figure 6-3):
• Finish-to-start (FS) This relationship means that Task A must be completed before Task B can begin. This is the most common relationship. For example, the foundation must be set before the framing can begin.
• Start-to-start (SS) This relationship means that Task A must start before Task B can start. This relationship allows both activities to happen in tandem. For example, a crew of painters is painting a house. Task A is to scrape the flecking paint off the house, and Task B is to prime the house. The workers scraping the house must start before the other workers can begin priming the house. All of the scraping doesn't have to be completed before the priming can start, just some of it.
• Finish-to-finish (FF) This relationship means that Task A must be completed before Task B is completed. Ideally, the two tasks should finish at exactly the same time, but this is not always the case. For example, two teams of electricians may be working together to install new telephone cables throughout a building by Monday morning. Team A is pulling the cable to each office. Team B, meanwhile, is connecting the cables to wall jacks and connecting the telephones. Team A must pull the cable to the office so that Team B can complete their activity. The activities need to be complete at nearly the same time, by Monday morning, so that the new phones are functional.
• Start-to-finish (SF) This relationship is unusual and is rarely used. It requires that Task A start so that Task B may finish. Such relationships may be encountered in construction and manufacturing. It is also known as just-in-time (JIT) scheduling. An example is a construction of a shoe store. The end of the construction is soon, but an exact date is not known. The owner of the shoe store doesn't want to order the shoe inventory until the completion of the construction is nearly complete. The start of the construction tasks dictates when the inventory of the shoes is ordered.
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What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.